TWI628226B - Polybutylene terephthalate resin composition - Google Patents

Abstract

The present invention provides a polybutylene terephthalate resin composition which is excellent in mold release property, metering stability, and hydrolysis resistance and which is small in color change in a high temperature environment. The polybutylene terephthalate resin composition comprises (A) polybutylene terephthalate resin, (B) higher fatty acid ester of pentaerythritol, and (C) low molecular weight polyethylene having a number average molecular weight of 3000 to 7000 . The component (B) is preferably pentaerythritol tetrastearate, and the component (C) is preferably a low molecular weight polyethylene having a number average molecular weight of 4500 to 5,500.

Description

Polybutylene terephthalate resin composition

The present invention relates to a polybutylene terephthalate resin composition; more particularly, it relates to a polybutylene terephthalate resin which is excellent in mold release property and metering stability at the time of injection molding. Composition.

Polybutylene terephthalate resin (hereinafter also referred to as "PBT resin") is improved in heat distortion temperature, and has good electrical properties, mechanical properties, weather resistance, and chemical resistance, and therefore becomes an engineering plastic. Widely used in various applications such as motors, electronic parts, and automotive parts.

Since the PBT resin is a thermoplastic resin, in order to obtain a molded article, an injection molding method is generally employed. The injection molding method is a method in which a molten resin composition is filled in a cavity of a mold heated to a temperature lower than the softening temperature to be hardened to form a cavity shape of the mold. After the molding, the molded article is released from the mold. However, when the molded article and the mold are strongly solidified, the mold is not easily released, or the molded article is broken or deformed when the mold is released. Therefore, in the injection molding method, it is extremely important to improve the mold release system. In order to improve the mold release property, an additive such as a release agent or a slip agent is usually added to the resin composition (for example, refer to Patent Documents 1 to 3).

On the other hand, when the injection molding method is used, for example, by granulating a resin composition containing a PBT resin and a lubricant, the pellet is put into the pellet. The funnel is injected into the molding machine, and the particles are ejected from the nozzle supply portion → the plasticizable portion → the metering portion, and are ejected from the nozzle into the cavity of the mold. In this state, when the conveyance at the supply portion or the melting of the plasticized portion is unstable due to any of them, the time required for measuring the resin required for each injection in the measuring portion is so-called unevenness. The problem.

Patent Document 1 describes a polyester resin composition comprising a thermoplastic polyester resin and a fatty acid ester. The improvement in mold release property, metering stability, and the like can be attained by the resin composition. As the above-mentioned fatty acid ester, a polyol selected from glycerin and pentaerythritol and a fatty acid having 12 or more carbon atoms are used. However, in the state in which a fatty acid ester having a reduced hydroxyl value (for example, pentaerythritol tetraerythritol) is used as a monomer, the measurement stability is deteriorated. Further, since the PBT resin has an ester group in the molecule, there is a disadvantage that the physical properties are easily lowered by hydrolysis in an environment of high temperature and high humidity. Therefore, it is required to improve the hydrolysis resistance, but the above-mentioned resin composition is not sufficient for hydrolysis resistance.

Patent Document 2 describes a styrene resin composition comprising (a) a styrene resin, (b) a higher fatty acid ester of pentaerythritol, (c) an ethyl bisstearylamine, and (d) Low molecular weight polyethylene. The improvement in mold release property can be attained by the resin composition, but measurement stability cannot be pursued.

Patent Document 3 describes a resin composition containing a predetermined polyester resin of a PBT resin and a lubricant containing at least one of a predetermined phosphate ester, montan wax, and polyethylene wax. It is possible to achieve an improvement in the rolling workability such as mold release property, sheet-out property, and pull-down property by the resin composition. However, in the review by the present inventors, it was found that the aforementioned resin composition was discolored in a high temperature environment.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 4-120162

[Patent Document 2] Japanese Patent Laid-Open No. Hei 8-169998

[Patent Document 3] Japanese Patent Laid-Open Publication No. 2008-222995

The present invention has been made in view of the above-mentioned problems of the prior art, and its object is to provide a polybutylene terephthalate which has good mold release property, metering stability and hydrolysis resistance and is small in color change under high temperature environment. Ester resin composition.

The present invention for solving the aforementioned problems is as follows.

(1): a polybutylene terephthalate resin composition comprising (A) polybutylene terephthalate resin, (B) higher fatty acid ester of pentaerythritol, and (C) number average molecular weight 3000~ 7000 low molecular weight polyethylene.

(2) The polybutylene terephthalate resin composition according to (1) above, wherein the component (B) is a pentaerythritol stearate.

(3) The polybutylene terephthalate resin composition according to (1) or (2) above, wherein the component (B) is pentaerythritol tetrastearyl ester.

(4) The polybutylene terephthalate resin composition according to any one of (1) to (3), wherein the component (C) is a low molecular weight polyethylene having a number average molecular weight of 4500 to 5,500.

(5) The polybutylene terephthalate resin composition according to any one of the above (1), wherein the component (C) is a linear polyethylene.

(6) The polybutylene terephthalate resin composition according to any one of the above (1) to (5), wherein the (B) is contained in an amount of 100 parts by mass based on the component (A). The component is 0.01 to 2.0 parts by mass and the above-mentioned (C) component is 0.1 to 5.0 parts by mass.

According to the present invention, it is possible to provide a polybutylene terephthalate resin composition which is excellent in mold release property, metering stability, and hydrolysis resistance and which is small in discoloration in a high-temperature environment.

1‧‧‧Test piece

11‧‧‧ tablet

12‧‧‧1st Die Resistance Department

13‧‧‧2nd Die Resistance Department

14‧‧‧ Highlights

Fig. 1 is a perspective view showing a test piece used in the evaluation of the release property in the examples.

The polybutylene terephthalate resin composition of the present invention is characterized by comprising (A) polybutylene terephthalate resin, (B) higher fatty acid ester of pentaerythritol, and (C) number average molecular weight of 3000 ~7000 low molecular weight polyethylene.

In the PBT resin composition of the present invention, the component (B) and the component (C) function as a lubricant, and by the combination of these lubricants, not only the mold release property but also the metering stability and water resistance can be achieved. The solution is good and it also inhibits the occurrence of discoloration.

Hereinafter, each component of the PBT resin composition of the present invention will be described.

[(A) PBT resin]

The PBT resin is a dicarboxylic acid component containing at least terephthalic acid or an ester-forming derivative thereof (alkyl ester of C _1-6 or fluorenyl halide, etc.) and at least an alkylene glycol having at least 4 carbon atoms ( A resin obtained by polycondensation of an ethylene glycol component of 1,4-butanediol or an ester-forming derivative thereof (such as an acetylated product). The PBT resin is not limited to homopolybutylene terephthalate, and may be a copolymer containing 60 mol% or more (particularly 75 mol% or more and 95 mol% or less) of butylene terephthalate unit. .

The amount of terminal carboxyl groups of the PBT resin is not particularly limited as long as it does not impair the effects of the present invention. The amount of terminal carboxyl groups of the PBT resin is preferably 30 meq/kg or less, more preferably 25 meq/kg or less.

The intrinsic viscosity (IV) of the PBT resin is preferably from 0.70 to 1.00 dL/g, more preferably from 0.72 to 0.95 dL/g, and even more preferably from 0.75 to 0.90 dL/g. The PBT resin composition obtained in the state in which the PBT resin having the intrinsic viscosity of such a range is used has particularly good flame retardancy and fluidity. On the contrary, when the intrinsic viscosity is less than 0.70 dL/g, good flame retardancy cannot be obtained, and when it exceeds 1.00 dL/g, good fluidity cannot be obtained.

Further, the PBT resin having an intrinsic viscosity of the above range may be blended with a PBT resin having a different intrinsic viscosity to adjust the intrinsic viscosity. For example, a PBT resin having an intrinsic viscosity of 0.8 dL/g can be prepared by blending a PBT resin having an intrinsic viscosity of 0.9 dL/g and a PBT resin having an intrinsic viscosity of 0.7 dL/g. The intrinsic viscosity (IV) of the PBT resin can be, for example, by a temperature of 35 ° C in o-chlorophenol. The measurement was carried out.

In the PBT resin, a dicarboxylic acid component (copolymer monomer component) other than terephthalic acid and an ester-forming derivative thereof may, for example, be an isophthalic acid, a phthalic acid or a 2,6-naphthalene dicarboxylic acid. a C _8-14 aromatic dicarboxylic acid such as 4,4'-dicarboxydiphenyl ether; a C _4-16 alkane dicarboxylic acid such as succinic acid, adipic acid, sebacic acid or sebacic acid; A C _5-10 cycloalkane dicarboxylic acid such as cyclohexane dicarboxylic acid; an ester-forming derivative of these dicarboxylic acid components (alkyl ester derivative of C _1-6 or mercapto halide, etc.). These dicarboxylic acid components can be used individually or in combination of 2 or more types.

Among these dicarboxylic acid components, C _8-12 aromatic dicarboxylic acid such as isophthalic acid and C _6-12 alkane dicarboxylic acid such as adipic acid, sebacic acid or sebacic acid are more preferable. acid.

In the PBT resin, examples of the ethylene glycol component (copolymer monomer component) other than 1,4-butanediol include ethylene glycol, propylene glycol, trimethyl glycol, 1,3-butylene glycol, and hexamethyl glycol. a C _2-10 alkylene glycol such as neopentyl glycol or 1,3-octanediol; a polyhydroxyalkylene glycol such as diethylene glycol, triethylene glycol or dipropylene glycol; An alicyclic diol such as hexane dimethanol or hydrogenated bisphenol A; an aromatic diol such as bisphenol A or 4,4'-dihydroxybiphenyl; and 2 ole of ethylene oxide of bisphenol A An epoxide addition product of C _2-4 of bisphenol A such as an adduct of an exemplified propylene oxide of bisphenol A; or an ester-forming derivative of these ethylene glycol; (Acetylamine, etc.). These ethylene glycol components can be used individually or in combination of 2 or more types.

Among these ethylene glycol components, a C _2-6 alkylene glycol such as ethylene glycol or trimethyl glycol, a polyhydroxyalkylene glycol such as diethylene glycol, or a cyclohexane is more preferable. An alicyclic diol such as dimethanol or the like.

As a series of comonomer components other than the dicarboxylic acid component and the ethylene glycol component, for example, 4-hydroxybenzoic acid, 3-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, 4-carboxy-4' can be used. An aromatic hydroxycarboxylic acid such as a hydroxybiphenyl group; an aliphatic hydroxycarboxylic acid such as glycolic acid or hydroxycaproic acid; propyl lactone, butyrolactone, valerolactone, and caprolactone (ε-caprolactone) C _3-12 lactones, etc.; ester-forming derivatives of ethylene glycols of these comonomer components (alkyl ester derivatives of C _1-6 , mercapto halides, acetylated hydrazines, etc.).

In the present invention, as described above, the PBT resin is used as the resin component series, but other polyester resins such as PET resin, PPT resin, PBN resin, and PEN resin may be used.

[(B) higher fatty acid esters of pentaerythritol]

(B) The higher fatty acid ester of pentaerythritol is as described above and functions as a slip agent. The higher fatty acid series derived from the component (B) is a fatty acid having 6 to 28 carbon atoms, specifically oleic acid, stearic acid, lauric acid, hydroxystearic acid, behenic acid, arachidonic acid, linoleic acid, Linolenic acid, ricinoleic acid, palmitic acid, montanic acid. Even among them, stearic acid, palmitic acid, and behenic acid are preferred.

The above-mentioned component (B) is preferably a stearic acid ester of pentaerythritol from the viewpoint of suppressing discoloration in a high-temperature environment.

Further, in the case of stearic acid stearate, from the viewpoint of improving mold release property, it is more preferably a full ester than a partial ester. That is, pentaerythritol tetrastearate is preferred.

In the present invention, the content of the component (B) is preferably relative to (A) The amount of the component is from 0.01 to 2.0 parts by mass, more preferably from 0.1 to 1.0 part by mass, per 100 parts by mass.

[(C) Low molecular weight polyethylene with an average molecular weight of 3000 to 7000]

The low molecular weight polyethylene having a number average molecular weight of 3,000 to 7,000 is similar to the component (B) and functions as a lubricant. More specifically, the effects of the present invention which have been described can be found by the combination of the component (B) and (C).

In the present invention, the number average molecular weight of the low molecular weight polyethylene of the component (C) is from 3,000 to 7,000. When the amount is less than 3,000, the measurement stability is deteriorated, and when it exceeds 7,000, the mold release property is deteriorated. The number average molecular weight is preferably from 4,000 to 6,000, more preferably from 4,500 to 5,500.

The molecular shape of the low molecular weight polyethylene as the component (C) is preferably a linear shape which is close to the branch and which is moderately entered from the viewpoint of improving thermal stability, strength, and mold release property. . When the branch is excessively small, there is a fear that the bleed out and the strength are lowered, and when the branch is excessively excessive, the effect of improving the mold release property becomes small.

In the present invention, the content of the component (C) is preferably from 1 to 5.0 parts by mass, more preferably from 0.2 to 3.0 parts by mass, per 100 parts by mass of the component (A).

Further, in the present invention, the content ratio (y/x) of the component (x) and the component (c) (y) is preferably 0.5 to 50.0, more preferably 1.0 to 20.0, particularly preferably 1.5. 10.

(other ingredients)

The PBT resin composition of the present invention may contain other components within the range which does not impair the effects of the present invention. As a series of other ingredients, inorganic filling An anti-oxidation agent such as a charge, a drip preventer, a hindered phenol, a phosphorus-based secondary oxidation preventive agent, a thioether-based secondary oxidation preventive agent, an inorganic crystal nucleating agent, a colorant, and the like.

[Examples]

Hereinafter, the present invention will be more specifically described by the examples, but the present invention is not limited to the following examples.

[Examples 1 to 4, Comparative Examples 1 to 11]

In each of the Examples ‧Comparative Examples, the parts (parts by mass) of the PBT resin and other components shown in Table 1 were blended by a 2-axis extruder having a spiral of 30 mm (Nippon Steel Works Co., Ltd.) The product, TEX-30), was melted, 260 kneaded and extruded at 260 ° C to obtain resin pellets.

The details of the foregoing components are as follows.

‧PBT resin: manufactured by WINTEC Polymer Co., Ltd., DURANEX (registered trademark) (inherent viscosity: 0.84 dL/g, terminal carboxyl group: 14 meq/kg)

‧ Pentaerythritol tetrastearate: Rikenster EW-440AT

‧ Trimethylolpropane montanate: Clariant Japan Co., Ltd., Licolub WE40

‧ glycerol tristearate: Polymorphic vitamin (stock) company, Poem S-95

‧ Polyethylene 1 (number average molecular weight: 5000, melting point: 105 ° C)

‧ Polyethylene 2 (number average molecular weight: 600, melting point: 59 ° C)

‧ Polyethylene 3 (number average molecular weight: 700, melting point: 72 ° C)

‧ Polyethylene 4 (number average molecular weight: 1500, melting point: 102 ° C)

‧ Polyethylene 5 (number average molecular weight: 2000, melting point: 102 ° C)

‧ Polyethylene 6 (number average molecular weight: 8000, melting point: 127 ° C)

Using the resin pellets of the respective Examples and Comparative Examples obtained as described above, the following tests (1) to (4) were carried out. However, in Examples 2 to 4 and Comparative Examples 5, 7 to 9, and 11, only (2) evaluation of measurement stability was performed. Further, in Comparative Examples 3 and 4, the evaluation of (3) discoloration was not performed. Further, in Comparative Example 10, only the evaluations of (1) to (3) were performed.

(1) Release

After the resin pellets of each of the examples and the comparative examples were dried at 140 ° C for 3 hours, the evaluation of the release property was carried out. The evaluation of the release property was carried out by an injection molding machine (manufactured by Toshiba Corporation, EC40) under the conditions of a cylinder temperature of 250 ° C, a mold temperature of 40 ° C, an injection speed of 20 mm/sec, and a holding pressure of 70 MPa. The test piece 1 which is formed by the flat plate 11 , the rib-shaped first die-releasing portion 12 and the cylindrical second die-resisting portion 13 protrudes from the protruding point 14 on the flat plate 11 by the ejection pin. The minimum cooling time (seconds) that can be protruded by three consecutive shots without deformation of the test piece was measured. The results are shown in Table 1. Further, the size of the flat plate 11 is 30 mm on the long side, 15 mm on the short side, and 1 mm in the thickness. The size of the first release mold portion 12 is 10 mm in height, 15 mm in width, 2 mm in thickness in the central thin portion, and 3 mm in thickness at both ends. The size of the second die-away portion 13 is 3 mm in the bottom surface and 7 mm in height.

(2) Measurement stability

The resin pellets of each of the examples and the comparative examples obtained as described above were placed in an injection molding machine (manufactured by Toshiba Corporation, EC40), and a flat plate of 65 mm × 55 mm × 2 mm was continuously formed, and between 200 injections, each measurement was performed. 1 spray The measurement time of the shot. In addition, the effect of the initial instability is removed. Therefore, the first 20 injections are discarded, and 200 injections after 20 injections are performed. As a measurement target, the average measurement time and the measurement time of one injection are more than 100 seconds. The number of injections. The results are shown in Table 1.

(3) Discoloration

The resin pellets of each of the examples and the comparative examples obtained as described above were placed in an injection molding machine (manufactured by Toshiba Corporation, EC40), and a rectangular test piece of 130 mm × 13 mm × 1.5 mm was formed by a gear oven. Dry heat treatment was carried out at 150 °C. The color difference ΔE was measured by a spectrophotometer (manufactured by Nippon Denshoku Industries Co., Ltd., SE6000) using each of the test pieces before and after the treatment for 300 hours. The results are shown in Table 1.

(4) Hydrolysis resistance

The resin pellets of each of the examples and the comparative examples obtained as described above were placed in an injection molding machine (manufactured by Toshiba Corporation, EC40), and a rectangular test piece of 130 mm × 13 mm × 1.5 mm was formed by a universal testing machine (Orientec). The initial value of the bending strength (MPa) was measured by the company system, RTC-1325A). Next, using a pressure cooker test (PCT) apparatus, after treating at 121 ° C and 100% RH for 50 hours, the bending strength (MPa) was measured in the same manner as the above-described measurement method, and the measured value and the initial value were used to obtain the retention. rate. The bending strength and retention ratio after initial treatment and PCT treatment are shown in Table 1.

【Table 1】

From the above Table 1, it was found that in Example 1, good results were obtained in all of the mold release property, the metering stability, and the hydrolysis resistance. In addition, only the average molecular weight of the polyethylene differs, except for the comparison between Example 2 and Comparative Example 5 of the same composition, and the presence or absence of polyethylene, except for Example 3 of the same composition. In comparison with Comparative Example 2, it was found that in the present invention, when a polyethylene having a number average molecular weight within a predetermined range is used, the metering stability is improved.

On the other hand, in Comparative Examples 1 and 2 in which no polyethylene was added, the mold release property was deteriorated. Further, in Comparative Examples 3 to 5 and 7 in which polyethylene having a number average molecular weight of less than 3,000 was used, the measurement stability was deteriorated. Further, Comparative Example 6 in which trimethylolpropane montanate was used alone gave good results in terms of mold release property, metering stability, and hydrolysis resistance, but discoloration occurred at a high temperature. Further, in Comparative Example 8 in which polyethylene having a number average molecular weight of more than 7,000 was used, the mold release property and the metering stability were deteriorated. Further, Comparative Example 9 in which no pentaerythritol tetrastearate was used was deteriorated in mold release property. Further, Comparative Example 10 in which trimethylolpropane montanate was used instead of pentaerythritol tetrastearate was found to have no problem in mold release property and metering stability, but discoloration occurred at a high temperature. Further, Comparative Example 11 in which glycerol tristearate was used instead of pentaerythritol tetrastearate deteriorated in mold release property and metering stability.

From the above evaluation results, it was revealed that the PBT resin composition of the present invention is excellent in all mold release properties, metering stability, and hydrolysis resistance.

Claims (6)

A polybutylene terephthalate resin composition comprising: (A) a polybutylene terephthalate resin, (B) a higher fatty acid ester of pentaerythritol, and (C) a low molecular weight of a number average molecular weight of 4500 to 5,500 The polyethylene contains 0.2 to 1.0 part by mass of the above-mentioned (B) component and 0.5 to 2.0 parts by mass of the above-mentioned (C) component, based on 100 parts by mass of the component (A). The polybutylene terephthalate resin composition according to claim 1, wherein the component (B) is a stearic acid ester of pentaerythritol. The polybutylene terephthalate resin composition according to claim 1 or 2, wherein the component (B) is pentaerythritol tetrastearate. The polybutylene terephthalate resin composition according to claim 1 or 2, wherein the component (C) is a linear polyethylene. The polybutylene terephthalate resin composition according to the first or second aspect of the invention, wherein the component (B) is contained in an amount of 0.2 to 0.5 parts by mass based on 100 parts by mass of the component (A). The polybutylene terephthalate resin composition according to claim 1 or 2, wherein the ratio of the content (y) of the component (C) to the content (x) of the component (B) is (y) /x) is 2.5~50.